New Results from D

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New Results from DØ
John Hobbs (Stony Brook) For the DØ
Collaboration
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This summer (since mid May) gt30
preliminary results 12 papers
submitted gt42 TOTAL from all physics
areas B physics, EW, Higgs, New Phenomena
searches, QCD, top physics Some have improved
techniques, some with increased luminosity,
some new topics, (and some a combination of
these)
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Discuss a subset of results all results
deserve fuller treatment no discussion for
results in recent WCs also see DØ
results area for full list and notes and
papers Thanks to my
DØ colleagues for all their hard work
First Observation of a New b-baryon ?b, June
15 Measurements of the Lb Lifetime _at_DØ, July
13 Top Quark Physics _at_DØ as a probe for new
Physics,
July 20
www-d0.fnal.gov/Run2Physics/WWW/results.htm
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Data Taking and Performance
Thank you, accelerator division!
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In this talk

• Foundation Physics from EW QCD
• Building blocks supporting other results
• Anomalous Couplings
• The top program
• Beyond-the-Standard-Model searches
• B Physics
• Higgs Searches

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EW QCD Results

• s(Wc-jets)/s(Wjets)
• ds/dpT(Z)
• s(WZ) and anomalous couplings
• Zg Production and anomalous couplings
• s(pp-gtZ)B(Z-gttt)
• Measurement of U(1S) U(2S) polarization

publication
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Foundation I W(c-jets)
1 fb-1
Dominant modes shown

• boson heavy flavor is crucial for continued
  improvement in Higgs search
• Want full program W/Zc, cc, b, bb
• 1st measurement of Wc-quark production
• Method
• Charge correlation between a lepton from charm
  decay and W lepton
• W m-tagged jet(s)

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Foundation I Wc
Charge symmetric background subtracted by SS
vs. OS comparison
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Foundation II pT(Z)
1 fb-1

• Test of theory
• both soft and hard QCD
• Generators for W mass, width,
• Previous limited yZ
• Now, up to yZ3
• Z -gt ee final state

Low pT(Z) tests resummation (Collins,
Soper, Sterman)
pT(Z)
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pT(Z)
Melnikov, Petriello PRD 74, 114017, )2006)
pT(Z)
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Foundation III Z-gttt
1 fb-1

• A number of results use hadronic t decays
• Measuring s(pp-gtZ) in Z-gttt cross checks our
  ability to identify hadronic t decays

Obvious physics benefit from cleanly
identifying hadronic decays
t Branching Fractions
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Foundation III Z-gttt
Method Use Z -gt tt -gt mth Signal
prediction Instrumental Bkg (from OS, SS)
s(pp-gtZ)B(Z-gttt) 247 8(stat) 13(sys)
15(lumi) pb
Increases confidence in our th results
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Anomalous Couplings
1 fb-1

• WWZ trilinear coupling (recently also, ZZg/Zgg)
• Assume an effective Lagrangian, and look for
  deviation from SM coupling values

(SM diagrams)
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Anomalous Couplings
Fit number of events and Z pT spectrum
Model independent and 2x better than
previous best (LEP)
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The Top Program
Mass, mt
Expected B(t-gtlvb)
Other states
Production rate, s
Couplings
Look for other particles masquerading in
production or decay (all tt all the time?)
W in-decay properties, e.g. helicity
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Top Physics New Results

• New Physics in Prod/Decay
• Search for stop in ttbar
• ttbar Charge Asymmetry
• W helicity in top decay
• ttbar resonance search
• s(tt ljets)/s(tt ll)
• Single top update

• Top Mass
• mt, dilepton MWT
• and combination
• mt from s(tt)
• Cross sections
• s(tt) in ltrk
• s(tt) in lth
• s(tt), dilep combinition
• B(t-gtWb)/B(t-gtWq) s
• Dilepton cross section
• ljets cross section

prev. WC
publication
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Top Program
?'s 14
all jet 46
lepton jets
Top decay - final states this discussion
primarily dileptons
dilepton
lepton jets
e/µ jet 34
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Top Program Improvements
1 fb-1
Mass, mt
Use template methods for mt in dilepton final
states
gt Compensate for underconstrained kinematics

• Update result w/matrix weighting method.
• Added ee and mm to existing em and improved
  selection,
• Combine with result from n weighting method

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Top Mass
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Top Mass

• Combine Matrix weighting result with neutrino
  weighting result (same data set)

Ensemble studies
mt 173.7 5.4 3.4 GeV
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Top Cross Section

• Recover lost acceptance in dilepton final states
  ltrack
• Use leptons which fail identification by finding
  a high-momentum, isolated track
• Orthogonal to standard ll

Gain additional 30 acceptance
ltrack only

• 6.2 (stat) (syst)
• 0.4 (lumi)

0.9 0.8 -0.9 -0.7
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Top Program
Top decay - final states Note historical
situation ts arent considered leptons for
top ?
Focus on an unexplored region, lt
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Top Program s(tt)B(tt -gt ltbb)

• Further expanding the program
• Look for deviation in t modes (from, e.g. H)
• About 2/3 of selected tt -gt lt is really from
  tt-gt ljets or tt -gt ll
• Consider cross-talk from other ttbar channels
  (e.g ljets with t fake) as background.
• Recompute cross section, moving other top
  contributions into background category

s(tt)B(tt-gtltbbnn) 0.19 0.08(stat)
0.07(syst) 0.01 (lumi) pb
SM, sB 0.126 pb
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Top Program Reinterpreting s
1 fb-1

• Use recent cross section measurements for
  additional information
• From measured values compute
• For a H, if MH MW and if B(H -gt cs) 1

s(tt), lj s(tt), ll
0.27 -0.26
R 1.21 (statsys)
e.g. in MHDM, radiative corrs. w/in MSSM,
B(t-gtHb) lt 0.35 (95 CL) expected, B lt 0.25
(95 CL), if B0
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Top Program Reinterpreting s
Looking at methods of measuring mt with
different implicit assumptions? Extract the
mass from the cross section
s(tt) from ljets channel
Measured
mt 166.9 (exp) (th)
5.9 3.7 -5.2 -3.8
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BSM Searches New Results

• t -gt c c0
• q search in th jets ET
• cc0 in trileptons, eel
• b -gt Zb, Long Lived Parents of Zs
• 3rd generation LQ in ttbb
• GMSB in gg
• t pairs in dileptons ET b-jets
• H -gt gg
• H -gt mm-mm-
• LQ3 in b-tagged jets ET

publication
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SUSY t -gt c c0
1 fb-1

• R-parity implies stop pair production
• For c0 as LSP, and
  . mc lt Mt-mc0 lt mW mb
• 2 (charm) jets plus MET in the final state

t -gt c c0
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SUSY t -gt c c0
Basic Preselection (partial list) then
flavor tag (gt 1 jet) mass dependent
optimization
HT (GeV)
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SUSY t -gt c c0
Composition W-gtlnjets 20.6 2.3 Z
-gtnnjets 13.2 1.8 W-gtlnHF 11.9 1.1
Z -gtnnHF 11.6 0.8 other 7.0
0.4 Total 64.3 3.2 Data
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use Z-gteejets to normalize Z-gtvvjets
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q Search in th jets ET
1 fb-1
1 or 2 ts in final state
(m0,m1/2)
here are ts again
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q Search in th jets ET
tan(b) 15, A0-2m0, mlt0
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SUSY Chargino/Neutralino -gttrileptons
0.91.7 fb-1

• New result in eel

After initial selection
After partial selection Pred. Bkg 208
7 Data 182
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SUSY trileptons
After full selection Signal 1-2 evts
Pred Bkg 1 0.3 Data 0
Limit moves from mgt140 GeV (all channels) to
mgt146 GeV
Depending on SUSY parameters
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B Physics New results

• Bs Mixing Update
• Search for Bsgt mm- Decay (1 fb-1 2 fb-1)
• Lb lifetime in semileptonic decay
• 1st Observation of Xb
• Direct CP violation in B -gt J/y K
• Search for FCNC in D mesons
• Observation of B

prev. WC
publication
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Mixing Whats in the Update?
2.4 fb-1

• More data 2.4 fb-1 (2x previous)
• Better detector Layer 0 silicon
• Track-by-track IP resolution uncertainty
• Same side flavor tagging (SST)
• Additional channel hadronic decays
• Better boost description

Experimentally demanding
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Mixing Two of the Improvements
Bs hadronic decays
Improved flavor tagging
Tag eD2 Old OST
2.5 0.2 SST
1.7 0.6 New OST 4.5
0.9 (evt charge) m trigger Dse, Dsp 22
5
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Mixing
Channels mfp efp
mKK pfp
2.4 fb-1 (Data thru end May)
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B Physics Direct CPV, B -gt J/y K

• Compare rates of opposite charge states

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B Physics Direct CPV, B -gt J/y K

• Possible at DØ, magnet polarity flipping
• Detector effects largely cancel

A 0.0067 0.0074 (stat) 0.0026 (sys)
1 sensitivity, 2x better than PDG
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Higgs Searches Whats New?

• Improved techniques (WH, ZH)
• NN in analysis and input to limit
• Separate into n-tags and k-jets
• Increased lepton acceptance (30, e)
• and more
• More luminosity
• WH, WW(partial) channels both with IIaIIb data
  samples.
• WH -gt WWW with IIa (1 fb-1)

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Higgs Searches New Results
11.7 fb-1

• Low Mass (MH lt 135 GeV)
• WH -gt lnbb
• ZH -gt llbb
• Intermediate Mass
• WH -gt WWW
• High Mass (MH gt 135 GeV)
• H-gtWW -gt mth
• H -gt WW -gt em

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Higgs Searches Low Mass
1-1.7 fb-1
WH -gt lnbb, Preselection
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Higgs Searches Low Mass
Variables pT,j1, pT,j2 DR(jj),
pT,dijets, MJJ, pT(l,MET)
Now using a NN for final stage. Fit NN output
for final result
NN output
No tag
1 b-tag
gt 2 b-tag
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High Mass H-gtWW-gtem
1-1.7 fb-1
Basic preselection then multivariate for final
stage
NN output
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Higgs WH Limit
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Conclusions

• DØ running well
• IIb average efficiency, 87
• using new Layer 0, L1 Cal trig.
• gt42 new results
• All major physics areas
• Broadening the program
• Improved techniques
• Up to 2.4 fb-1 in analysis
• Yet essentially all are statistics limited

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BACKUP
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Top Mass
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Top Program Cross Section Decay
1 fb-1

• Simultaneous measurement of s(tt) and
  RB(t-gtbW)/B(t-gtqW) in ljets channel
• Predict b-jet multiplicity as function of R
• Use ljets channel
• Overall yield and
• 0, 1 and 2-tag yields

Fit yields as function of s and R
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The results
Most precise measurements of R and s (by
fractional uncertainty)
(Kidonakis Vogt)
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Top Program s(tt)
1 fb-1

• previously measured cross section in all channels
  except tt -gt lthnnbb. First, assume SM

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Squarks -gt taus jets MET
t
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Top Mass
Matrix weighting
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Mixing Effect of each improvement
How does sensitivity evolve? 1.3 fb-1, mfp
14.1 ps-1 scale factor 16.1
SST (comb) 19.9 k-factor
20.0 1.1 fb-1 24.4
semi-leptonic hadronic
mfp mode (stats) only
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Mixing New Layer 0 Silicon
Located at R0.75 - improved IP resolution -
coverage (SMT aging)
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Mixing Same Side Tagging

• Cannot use PID (K vs p)
• Optimize using other variables. Best are used in
  SST
• Closest track, f(dR)
• All tracks in Bs jet, S((qpT)0.6)/S(pT0.6)

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Mixing Yields
Hadronic yield low, but have high weight